Electrical system



Nov. 28, 1950 o. B. sHAFr-:R ET Al.

ELECTRICAL SYSTEM Filed May 9, 1945 N SRA REV @E AH THL N Nsu R E .S .O wf w A Y B l Patented Nov. 28, 1950 ELECTRICAL SYSTEM Orville B. Shafer, Owego, and John J. Sullivan, Binghamton, N. Y., assignors to International Business Machines Corporation, New York, N. Y., a corporation of New York Application May 9, 1945, Serial No. 592,778

3 Claims.

This invention relates to gaseous discharge tubes and related circuit means.

An object of the invention is the provision of a new form of gaseous discharge tube.

An object of the invention is the provision of a novel gaseous discharge tube especially serviceable as a comparing device.

An object of the invention is the provision of agaseous discharge tube of such inherent construction as to lend itself to utilization in a circuit arrangement for comparing electrical effects with respect to their time of occurrence.

Another object of the invention is the provision of a gas-filled tube which is so constructed as to lend itself to utilization in an indicia comparing circuit, wherein the indicia may be manifested by timed electrical pulses.

Other objects of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of examples, the principle of the invention and the best mode, which has been contemplated, of applying that principle.

In the drawings:

Fig. 1 is a partially diagrammatic view of a tube construction exempliying the principle of the invention.

Fig. 2 is a circuit diagram of a data comparing circuit involving the new form of tube.

The new form of gas-filled tube differs from the prior art in that it is provided with dual cathodes in combination with a single anode. Preferably, a grid is also used in combination with the dual cathodes and the anode. The tube is gassed with a low potential gas; i. e., one which, when conducting has a low voltage drop. A suitable medium is xenon gas cr one having substantially similar characteristics. Actually, a tube embodying the invention was gassed with mercury which is readily available and has the desired characteristics.

In the exemplification of the new form of tube shown in Fig. 1, the dual cathodes are elongated hollow rods, indirectly heated. One of the cathodes is designated KI and the other is designated K2. The cathodes are placed relatively close together and are surrounded by apgrd G in the form of a helix. The plate P is constructed as a hollow cylinder and surrounds the grid. lMercury vapor was used as the gaseous medium. The actual spacing between the centers of the cathodes, in the tube which was constructed, was about 0.075". The cathodes were coated with a mixture of barium and strontium oxides. Two filaments, one for each cathode, were connected in parallel to a source of 6.3 volts and the current' through each ltment was about 0.3 amp. The mercury was at saturated vapor pressure, and actual pressure, dependent on the temperature of the tube, ranged from 10 to 30 microns.

The characteristic feature of the tube is that either of the two cathodes may serve, upon application of a voltage across them, as a starteranode to re the tube and bring about the flow of electrons to the common plate. The plate is capable of receiving a flow of electrons suicient to operate a work relay in the plate circuit. Adequate negative bias is applied to the grid to prevent the plate voltage acting as the firing potential.

Fig. 2 indicates a typical circuit with which the tube may be used. The sensitivity of the tube will depend to some extent on the circuit constants. Resistance values which may be used are noted in Fig. 2. It is seen that each of the cathodes Kl and K2 is individually connected by a 200 ohm resistor to the minus side VM of a 40 v. line. The grid G is connected via a 0.5 meg. resistor to the minus sine of a 10 v. battery E. The plus side of the battery is connected to the minus side VM of the 40 v. line, so that the negative grid bias is approximately 10 volts, and is adequate to prevent the tube from being triggered by the voltage across the plate and cathodes. The plate P is wired to a work relay CR which is connected via normally closed cam contacts HC to the plus side VP of the 40 v. line.

Cathodes KI and K2 are individually connected by related 200 ohm resistors to plug sockets Pl-' and PP2. These may be plugged to sockets PI and P2 at a pair of indicia sensing stations #l and #2. Records are to be fed through these stations in synchronism. These records may be tabulating cards, perforated tapes7 code tapes, and so on. The records at stations #l and #2 are designated Tl and T2, respectively. A sensing brush Bl at station #l is adapted to engage, through a perforation in the record TI, with a contact roll CI. Similarly, a brush B2 at station #2 is adapted to engage, upon the passage of a perforation in record T2, with a contact roll C2. The sensing brushes BI and B2 are in circuit with plug sockets Pl and P2, respectively. The brushes IC and 2C are wired to common circuit breaker contacts CC which intermittently connect the brushes to the plus side VP of the 40 v. line. The contacts CC are timed to operate in synchronism with the passage of the records through the sensing station, in such manner that the contacts will make each time a perforation posi- 3 tion or index position, as it is usually called, passes under a sensing brush. Thus, if in a cyclic period of operation, twelve such index positions are adapted to pass under a sensing brush, the contacts will make at twelve similarly timed intervals. Each make interval of the contacts CC is shorter than the duratiorl oi passage of a' perforation under a sensing brush, so that thel make and break of a sensing circuit will be timed by contacts CC.

When a perforation in record TI is under the,

brush Bl, a sensing circuit is established from the plus side VP of the 40 if'. line' via contacts CC, the brush IC and contact roll C I, the brush BI, the plug connection between sockets PI and y PPI, and the 200 ohm resistor connected to cathode KI, to the minus side VM. This sensing circuit impresses approximately 40 volts on the cathode KI. Similarly, when a perforation in record T2 traverses the sensing brush B2, a.

sensing circuit is established for impressing ap'- proximately 40 volts on the cathode K2. If the perforations in records TI and T2'v are simultaneously' sensed, both the cathodes KI and K2 are raised concurrently to the same voltage, with the result that there isvno voltage difference between thev cathodes. Under this condition, the tube remains non-conductive. But if a perforation is sensed at one station and not, at the same time, at the other station, approximately 40 volts will be impressed on only one of the catho'des. Upon the occurrence of this voltage difference between the two cathodes, the gas ionizes and the tube res. In other words, if cathode KI alone is receiving approximately 40 volts, then it serves as a starter-anode and causes the tube to re. It cathode K2 alone is receiving such voltage, then it serves as the starter-anode and res the tube. If neither cathode is energized or if both are simultaneously energized, the potential across the cathodes is zero and the tube does not nre. It is seen, therefore, that the tube is so constructed as to possess the inherent capability of serving as a comparing device.

Upon the ring ofthe tube, current flows from the plus side of the 40 v. line via the normally closed contacts HC, the work relay CR, and through the tube to the minus side of the line, energizing the relay. The voltage drop in the anode-cathode circuit of the tube when conductive, and with the particular work relay absorbing approximately' 30 volts, was about l0 volts. The tube remains conductive until the plate potential is removed by the opening of cam contacts HC. These contacts will open once in each cyclic period, after the sensing times provided in such period.

rlf'he arrangement described above may be used for comparing data on record cards. Such data may be digits, for example, designated accord-` ing to the well-known Hollerith code. Another use to which the arrangement may be put is in detectingv the synchronism in travel of thek records at their respective stations. For instance, the records may he provided with small perforations in corresponding predetermined vertical positions, so that if the records icl-3d in synchronism, these perforations should simultaneously pass under the sensing brushes. But if the records do not stay in synchronism, then the perforations will not be sensed simultaneously. Consequently, one of the cathodes will have' a greater potential than the other,` and the tube will, fire. The relay CR willberv energized and may serve toV interrupt record feed or produce some other manifestation of the lack of synchronism of the records.

In effect, the described arrangement compares signals derived from perforated record material. The tube may serve generally to compare any pair of electrical signals. For example, Fig. 2 showsV two signal input lines A and B associated with detector-amplifier units AA and BB, respectively, each having a signal output of 40 v. The outputs of units AA and BB are connected to sockets. AP and BP which may be plugged to sockets PPI and PP2. The operation of the tube in comparing the' signals will be the same as described for the comparison of pulses timed by the means at stations #l and #2. It is to be noted, further, that a signal pulse coming from a detector-'ampliiier unit may be compared with a record-controlled pulse. For instance, if the pulses irom unit AA are to be compared with the pulses produced at station #1, the plug socket AP and PI will be' plugged to the sockets PPI and FP2.

While there have been shown and described and pointedV out the fundamental novel features of the invention'as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art,r without departing from the spirit of the invention. It is the intention, therefore, to be limited only Aas indicated by the scope of the following cfaims.

What is claimed is:

l. A gaseous discharge tube containing a low voltage gas, a single plate, a blocking grid, and a pair of similar cathodes individually connectable to separate sources of potential and symmetrically disposed with respect to the plate and rigidly arranged in parallel spaced relation, said cathodes being interchangeably effective, either cathode when at a suitable potential above the other cathode serving as a starter anode to ionize the gas for conducting electrons from the latter cathode to said plate.

2. Any electrical system including a gaseous `dis charge tube normally in non-conductive status and containing a. common plate, a blocking grid, and a pair of cathodes, either of which when at a suitably higher potential than the other serving as a starter anode to re the tube and render it conductive, a plate circuit including a source' of plate potential, a grid biasing circuit, a source of control potential coupled to one of the cathodes, and a source of similar control potential coupled to the other cathode, whereby upon concurrent application of such control potentials from the different sources the cathodes remain at substantially the same potential and the tube, thereby, remains non-conductive, and whereby upon application of the control potential to either one of the cathodes alone from the as,- sociated source this cathode serves as the starter anode to re the tube and render it conductive.

3. An electrical comparing system including a gaseous discharge tube containing a common plate and a pair of cathodes effective upon oc.- curr'ence of a sucient potential across theni to fire the tube and render it conductive, a plate circuit including a source of plate potential, a pair of sensingr devices for sensing a pair of record strips for intelligence designations, each upon sensing a designation passing through a similar potential, and Vmeans coupling each of the cat-nodes to a different one of the sensing devices REFERENCES CITED The following references are of record in the file of this patent:

Number 6 UNITED STATES PATENTS Name Date De Forest Jan. 11, 1921 Nicolson Mar. 23, 1926 Rollinson Mar. 6, 1928 Honaman Jan. 4, 1938 Heising Dec. 12, 1939 McCarthy July 29, 1941 Dench Jan. 13, 1942 

